uri is the URI to bind to. This is
normally of the form ‘druby://<hostname>:<port>’ where
<hostname> is a hostname of the local machine. If nil, then the
system’s default hostname will be bound to, on a port selected by the
system; these value can be retrieved from the uri attribute.
‘druby:’ specifies the default dRuby transport protocol: another
protocol, such as ‘drbunix:’, can be specified instead.

front is the front object for the server, that is, the object to
which remote method calls on the server will be passed. If nil, then the
server will not accept remote method calls.

If config_or_acl is a hash, it is the configuration to use for
this server. The following options are recognised: